In response to recent social demands and trends in the context of energy and environment problems, fuel cells capable of operating even at ordinary temperature and obtaining high output density have attracted attention as a power supply for an electric car and a stationary power supply. A fuel cell is a clean power generation system in which an electrode reaction product is water in principle and which reduces the load on the global environment. In particular, a polymer electrolyte fuel cell (PEFC) is expected as a power supply for an electric car because it operates at relatively low temperature.
A polymer fuel cell includes a membrane electrode assembly (MEA, hereinafter referred to as MEA) having an electrolyte membrane, catalyst layers provided on both surfaces of the membrane, gas diffusion layers (GDLs), and so on. A plurality of MEAs are stacked with separators being disposed therebetween to constitute a fuel cell.
Examples of known technologies for making electrode catalyst layers on both sides of an electrolyte membrane when making a MEA include a method of applying catalytic ink to an electrolyte membrane by using a screen printing apparatus (see, for example, PTL 1).
A screen printing apparatus includes a screen plate, in which an opening for forming a print pattern is formed; a scraper that is slidable over the screen plate; and a squeegee that is slidable over the screen plate as the scraper is. By sliding the scraper over the screen plate, ink on the screen plate is spread and the opening is filled with the ink. Subsequently, by sliding the squeegee over the screen plate while pressing the screen plate against a workpiece, the ink, with which the opening is filled, is transferred to a surface of the workpiece.
A scraper described in PTL 1 includes a guide for scraping ink. With the guide, ink is prevented from flowing beyond a movable range of the scraper when the scraper slides.